On roof antennas for vehicles, the antenna rods are designed with externally thread bases and matching mounting parts designed as threaded bushings are located inside the cover, into which elements the antenna rods are screwed. The following descriptions are limited to this most common embodiment, while an embodiment exists in which the inside of the antenna rod comprises an internal thread and the cover has a matching counterpart with a threaded pin, to which the invention is also applicable. Accordingly, the invention is applicable to any other conceivable connection of the antenna rod to the cover, such as a plug connection of the antenna rod to the cover etc.
The bushing, which is typically made of metal, on the one hand serves the function of fixing the antenna rod mechanically to the cover and of absorbing forces applied to the antenna rod during vehicle operation, and on the other hand serves to transmit the electrical signal from the antenna rod through the cover into the inside of the roof antenna, where it is typically picked up by a contact spring mounted on a printed circuit board for further electronic processing. So as to fix the bushing in a stable and waterproof way in the cover, the threaded hole is designed as a tapped blind hole and the bushing is typically incorporated as an insert during manufacturing of the cover in a plastic injection molding process.